CAMBRIDGE—A Harvard professor has identified what appears to be a scrap of fourth century Egyptian papyrus that contains the first known explicit reference to Jesus as married, a discovery that could fuel the millennia-old debate about priestly celibacy in the Catholic church.

The fragment, which has been preliminarily authenticated but still must undergo further testing, portrays Jesus as referring to a woman as his legitimate disciple—most likely his wife, whom the text’s author probably believed to be Mary Magdalene.

The text is not evidence Jesus was married, said the professor, Karen L. King, a historian of early Christianity at Harvard Divinity School, who is scheduled to discuss her discovery at an international gathering of Coptic scholars in Rome on Tuesday. But she said it may cast new light on the history of early Christianity, including the formation of Christian views of celibacy and whether women were members of Jesus’s inner circle, issues still intensely relevant to the Catholic church, which allows only celibate men to be priests.

“The issue has far from gone away,” King said.

The fragment is smaller than a business card, and appears to have been torn from the middle of a page of a codex, or primitive book, written in a southern Egyptian dialect. Its owner, who declines to be identified publicly, does not know where it was found.

It contains just eight broken lines, scrawled in a crude Coptic hand.

The fourth says: “… Jesus said to them, ‘My wife….”

The next line reads: “…she will be able to be my disciple.”

The text does not prove that Jesus had a wife, King emphasized. Even if it is actually a translation of a second century Greek text, as King theorizes, it would have been composed more than a century after the death of Jesus. The earliest and most reliable information about the historical Jesus is silent on the question of his marital status, King said.

“It’s not saying we’ve got the smoking gun that Jesus is married,” she said.

But the fragment—which King provocatively calls “The Gospel of Jesus’s wife”—does show that some early Christians believed Jesus was married, probably to Mary Magdalene, a follower of Jesus who the gospels say was the first person to see him after his resurrection.

It contains echoes of other early Christian writings, suggesting to King that it may have been part of a debate about the spiritual importance of celibacy verus marriage.

“The entire question about whether Jesus was married or not first arose only 150 years after Jesus died in the context of Christians discussing ... whether Christians should marry or remain celibate,” she said. “And that’s interesting.”

The fragment appears to underscore the diversity of Christian ideas about Jesus’s life when the faith was still in its infancy, before the books of the New Testament had been canonized and religious councils convened to resolve differences over beliefs.

“It helps to remind us that practically everything that later generations told about Jesus was put together and edited by somebody well after his death, and represents the view of Jesus that they were trying to get across,” said Roger Bagnall, director of the Institute for the Study of the Ancient World and professor of ancient history at New York University, who helped King authenticate the papyrus.

“It’s not going to change history in a dramatic way,” he said, “but it does give us a much sharper view of one little corner of Christianity we couldn’t see into before.”

The notion that Jesus may have been married, considered heretical by the Catholic church, has long captivated artists and conspiracy theorists. The success of Dan Brown’s 2003 international best-seller, “The Da Vinci Code,” which posits that the Catholic church covered up the marriage and progeny of Jesus and Mary Magdalene, testifies to its potency in the popular imagination.

Aware of the incendiary nature of her finding, and its potential for being dismissed as a forgery or distorted as evidence that Jesus was married, King has treated it a bit like academic dynamite.

Reporters for three publications—the Globe, the New York Times, and Harvard Magazine—were invited to a joint interview last week in King’s office, a book-lined nook with arched, leaded-glass windows on the top floor of Andover Hall. Each promised not to publish until 1 p.m. Tuesday, when King was scheduled to speak at the Institutum Patristicum Augustinianum, across the street from the Vatican.

The reporters were allowed to contact Bagnall and two other scholars who had helped authenticate and interpret the fragment, AnneMarie Luijendijk, a papyrologist and professor of religion at Princeton University who contributed to King’s paper, and Ariel Shisha-Halevy, a Coptic linguist at Hebrew University in Jerusalem. Reporters were not allowed to discuss King’s finding with other scholars in advance of her presentation at the Coptic Conference, the International Association for Coptic Studies.

Yet King decided to publicize her discovery before completing testing on the composition of the ink on the fragment. Such testing, which she plans to finish before the scheduled publication of her article in the January issue of the Harvard Theological Review, would not definitively date the fragment but could ensure that the chemicals in the ink matched what scribes in southern Egypt would have used in the 4th century.

But because so many people involved in the authentication process have now seen it, King feared word could leak out about its existence in a way that sensationalized its meaning. A more controlled release, she surmised, might raise the level of discussion about it. Major discoveries such as this are often brought forth at the Coptic Conference, she added, which meets once every four years—this year, by happenstance, in Rome.

And evidence of its authenticity was strong enough to make her think it was time to invite other scholars to weigh in, she said. In any case, she added, she stood to gain little if she was wrong.

“This is not a career maker,” said King, a tenured professor at Harvard. “If it’s a forgery, it’s a career breaker.”

* * *

Two of three anonymous scholars tapped by the Harvard Theological Review to review King’s 52-page paper cast doubt on the fragment’s authenticity, relying on low-resolution images to reach their conclusion. But both recommended that King bring the papyrus to an expert papyrologist. Neither knew King had already done so, having taken it to Bagnall. One of these reviewers also raised some questions about its grammar, but King said she and Shisha-Halevy were able to address those.

“I have no competence at all to decide whether this fragment is authentic or not,” Shisha-Halevysaid in a phone interview. But, he said, a couple of linguistic constructions pointed to by the reviewer “do not warrant considering this fragment a fake. Even if they are not usual … they are good Coptic.”

King said the owner of the papyrus wishes to remain anonymous because he does not want to be hounded by people who wish to buy the papyrus, which he has now offered to give to Harvard as part of a purchase of his collection of Greek, Coptic, and Arabic papyri. Harvard has not decided whether to pursue the offer.

* * *

It was a stranger’s e-mail that alerted King to the existence of the fragment. The man wanted to know whether the professor could help translate an ancient Coptic papyrus in his collection.

The man told King he had an inkling from a previous owner that it might say something about Jesus being married. When King looked at the photo he sent, the words leapt out at her immediately.

But was it authentic? Or a fraud?

“In this field, we keep having these things appear,” she said. “So I think it’s almost a reflex to be suspicious.”

King put it aside; she was busy with other projects. Last summer, the owner asked her a second time to take a look.

She stared at the photos again. This time, she spotted textual similarities to two other early Christian writings, the Gospels of Mary and Thomas.

King relented. She would look more closely, she told the owner, if he agreed to allow her to properly authenticate it. She needed to see the actual artifact. In December 2011, the man hand-delivered the papyrus to Harvard.

King needed as much information as possible about its origins, but the owner did not have much. He did not know, he said, where the fragment was found. All he had were a letter and a note, copies of which he e-mailed to King, addressed to the previous owner, an H.U. Laukamp, who had a Berlin address.

The letter to Laukamp, dated July 1982, from Peter Munro, a professor at the Free University of Berlin, states that his colleague, a Professor Fecht, had seen examining Laukamp’s papyrus collection.

The note—undated, unsigned and written in German—stated that Fecht believed this “small fragment … is the sole example of a text in which Jesus uses direct speech with reference to having a wife.”

King sent photos of the papyrus to Bagnall, who showed it to a small group of papyrologists he meets with regularly.

“We put it up on the screen and we all sort of said, ‘Eeew,’ ” said Bagnall, one of the world’s leading papyrologists. “We thought it was ugly. And it is ugly. The handwriting is not nice—thick, badly controlled strokes made by somebody who didn’t have a very good pen.”

Was it genuine? Bagnall, too, needed to see it.

In March 2012, King tucked the papyrus into her red leather bag along with her iPad and boarded a train to New York, where she and Luijendijk, a former student of King’s, met Bagnall at his office. They sat for several hours around a table, looking at the fragment under magnification and different kinds of light, noticing different details and talking through possible scenarios.

The fibrous, dual-layered material was clearly papyrus, an ancient Egyptian precursor to paper made of the pith of a plant that grew along the Nile. It seemed to be ancient; the pith, which makes the smooth writing surface, had worn off, along with the ink, on one side. They could see a spot where a tiny insect appeared to have nibbled at the surface.

Ancient papyrus is available for purchase on the antiquities market, however, so King and her colleagues had to figure out whether the ink was applied in ancient times or by a modern forger.

Infinitesimal details suggested it was genuine: Tiny fibers shredding from the sides of the paper contained almost invisible traces of ink from lost letters. Damage to fibers after they had been inscribed suggested the ink had been laid on the surface long ago, not recently.

The handwriting, workmanlike and laid on with a nubby pen, seemed to date to the 4th century. Its irregular, blocky script is more common in private letters—and quite unusual for a literary text, Bagnall said. But it is also plausible, he said, that it was the work of an unskilled scribe with a poor pen.

All in all, Bagnall said, “The preponderance of evidence is clearly in favor of authenticity, both because it is so hard to imagine who could have faked it and how, but also because there is nothing inherently suspect about it,” Bagnall said. “You’ve got the physical object, the handwriting, the language, and the content. There’s not a single one of those that seems to me suspect.”

When King and Luijendijk emerged from Bagnall’s office, they headed toward the subway to the train station. King joked: “The fragment gets a cab.”

King, who grew up in rural Montana, and Luijendijk, a Dutch scholar, had begun to believe they had stumbled across something extraordinary.

On the way back to Cambridge, King was a little more careful with her red leather bag.

* * *

King’s next task was to determine what the papyrus said—and what it meant. Because the text has no margins, each line is missing a beginning and ending. King used other ancient Christian texts as guides.

She believes that the context of the eight lines on the front side of the papyrus reflects a discussion Jesus was having with disciples about the “the cost of discipleship,” or how becoming a Christian may affect bonds with one’s natal family, similar to passages in Matthew and Luke.

This, she said, was a preoccupation of early Christians at a time when becoming a follower of Jesus meant risking persecution, King said.

“Becoming a Christian means joining a new family, and that may mean leaving your natal family behind,” she said.

The papyrus contains echoes of several other non-canonical gospels dated to the 2nd century, including the Gospels of Mary, Thomas and, especially, Philip, which also discuss discipleship – and seem to hint that Jesus was married to Mary Magdalene.

King said she and other scholars have argued previously that these references were metaphorical, meant to suggest that Jesus had a close spiritual bond with Mary Magdalene.

But the explicit reference to Jesus as married in “The Gospel of Jesus’s Wife” suggests to King that the second century writers may not have been speaking figuratively.

The papyrus, together with other writings from the period, suggests that second century Christians were arguing about Jesus’s marital status as part of a debate about whether they themselves should marry, and whether one had to be celibate to be a good Christian.

None of this, King said, affects what scholars know about the historical Jesus. The earliest, best information about him, contained in the gospels of the New Testament, says nothing about whether he was married or not. So it is impossible, she says, to know for sure.

If Jesus were married, King said, it is unlikely his wife would have been Mary of Magdala. Although she is portrayed in the gospels as a close follower of Jesus, women during that period were almost always identified by their relationship to a man. That she is always identified by her hometown makes it unlikely that the writers of the early gospels would have failed to mention such a salient fact.

But the issue may still be important to Christians today—for example, in debates about the celibate, all-male priesthood. King said she believes some may use this discovery “to say this allows us to speak theologically about … marital sexuality in a more positive way.”

Luijendijk said the papyrus paints a fuller picture of the variety of beliefs among early Christians, illustrating once again that Orthodox Christianity did not proceed in a neat line from the birth of Jesus Christ to the present day, she said. And theological differences over marriage, asceticism and sexuality had important implications that still resonate today.

“I expect that people will use this new text to bring up those questions again,” she said.